High-speed serial interface for orthogonal frequency division multiplexing (ofdm) cable modems

ABSTRACT

A high-speed serial interface (HSIF) for communicating between an analog front end (AFE) and a System on a Chip (SoC) digital radio via a bi-directional serial bit connection for an OFDM cable modem includes generating Status Frames and Data Frames to be communicated between the tuner and AFE and sending the generated Status Frames and Data Frames on a continual basis. Each Frame is a 10-bit K.28 Comma Sync word followed by a payload and when no data is queued to be communicated, Status Frames are sent asynchronously as filler frames.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims benefit of priority under 35 U.S.C. § 119(e) toco-pending U.S. Patent Application Ser. No. 62/547,515 filed Aug. 18,2017 by the same inventors and title as the present application, andwhich is fully incorporated herein by its reference.

FIELD

Embodiments of the present invention relate generally to, but notlimited to, communication architectures and methods for communicationsbetween an analog front end (AFE) circuit and a digitalmodulator/demodulator system on a chip (SoC).

BACKGROUND

Certain communication systems use orthogonal frequency divisionmultiplexing (OFDM), sometimes referred to as discrete multi-tone (DMT)transmission. One example of such OFDM communication system is definedby Data Over Cable Service Interface Specification (DOCSIS) 3.1,although the inventive embodiments are not limited thereto. A DOCSIS 3.1cable modem is customer premises equipment (CPE) that facilitates acustomer's, end-to-end digital communications with a network via a highfrequency OFDM waveform propagated over a medium such as coaxial cable,fiber or potentially over-the-air (OTA). The cable modem includes bothdigital processing and “front-end” (i.e., first part of a receiver ortransmitter interfaced with the transmission medium) analog processingcomponents to accomplish this. Generally, for example, in a receiver,analog circuitry is used to amplify/de-amplify and frequency-convertsignals so that they reach a suitable state to be converted into digitalvalues, after which further signal processing can be performed in thedigital domain.

With advances in the design and manufacture of integrated circuits (ICs)more and more traditional analog intermediate frequency (IF) signalprocessing tasks are handled digitally. Traditional analog tasks, likefiltering and up-down conversion are now handled by means of digitalfilters and digital signal processors (DSPs), sometimes referred to, notnecessarily identically because of design choices, as digital radioprocessors, digital tuners, baseband processors, etc. It is noteworthythat many com systems have “mixed” signal processing designs wheresignals are processed in both analog and digital domains.

The migration of analog into digital circuits means that the choice ofwhat front-end functions are implemented by analog and digital meansgenerally is discretionary with a system architect and selected based onfactors such as required performance, cost, size, and power consumption.Because of the mix of analog and digital technologies, OFDM transceiversgenerally have an analog front end (AFE) and a separate, digital radioprocessor/tuner to provide PHY and, if desired, medium access control(MAC) data link layer processing. In this case, the AFE and the digitaltuner must have a data interface to accomplish downlink and uplinkcommunications. Moreover, since manufacturers of analog components maydiffer from those providing digital tuner components, a common interfaceshould be fast, dependable, standardized/uniform and/or known to others.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

Certain circuits, logic operation, apparatuses and/or methods will bedescribed by way of non-limiting example only, in reference to theappended Drawing Figures in which:

FIG. 1 shows a basic network diagram in which example embodiments of theinvention may be utilized;

FIG. 2 shows a functional block diagram of a communication deviceaccording to various embodiments of the invention;

FIG. 3 shows a process for communicating OFDM channels between an analogfront end (AFE) and digital radio according to one or more embodimentsof the invention;

FIG. 4 shows a functional block diagram of an OFDM transceiver accordingto other embodiments;

FIGS. 5 and 6 show illustrative examples of downstream data and statusframes according to various embodiments;

FIGS. 7 and 8 show illustrative examples of upstream data and statusframes according to various embodiments; and

FIG. 9 shows an example functional block diagram of an OFDM-enabledmodem with high speed serial interface according to one or moreembodiments of the invention.

DETAILED DESCRIPTION OF THE INVENTION

While reference to example embodiments of the invention may be made tocable modems and related specifications, such as DOCSIS® 3.1 by CableTelevision Laboratories, Inc., the high-speed serial interface of theinventive embodiments are not limited thereto and may be used in anyprotocols, applications or architectures where similar principles may beapplied and their use provides similar advantages. Thus the specificdescription herein is provided only in context of one exampleimplementation and the claims within are in no way limited thereby.

As shown in FIG. 1 below, a basic network 100 is shown with a networknode 110, such as a cable provider Cable Modem Termination System (CMTS)or Internet service provider, which provides web access via an internetprotocol (IP) interface to end user terminals 122, 124 includingpersonal computers, laptops, wireless access points, via a networkconnection 112, such as a combination of optical fiber from a serviceprovider head end to an exchange terminal, transformed from optical toelectrical signals and delivered to end users, generally over a coaxialcable though inventive embodiments are in no way limited to anyparticular network configuration. In order to receive, demodulate, andaccess signals from network node 110 in the downstream via connection112, end user terminals 122, 124, 126 may require customer premiseequipment (CPE) such as a cable modem (CM) 115.

A cable modem termination system or CMTS 100 is a piece of equipment,typically located in a cable company's headend or hubsite, which is usedto provide high speed data services, such as cable Internet or Voiceover Internet Protocol, to cable subscribers by way of their CM.

Referring to FIG. 2, a functional block diagram of a cable modem (CM)having a high-speed serial interface (HSIF) according to one or moreinventive embodiments will now be explained. A cable modem 200 accordingto certain example embodiments, may include an analog front end (AFE)module 210 and a digital radio processor module 220. A high-speed serialinterface 224 provides 8b/10b encoded data and status framing betweenthe analog and digital modules 210 and 220. Optionally, digital tunermodule 220 may include MAC layer functionality 250 as well.

In certain embodiments, the modem 200 and high speed serial interface(HSIF) between AFE 210 and digital radio 220 may support DOCSIS 3.1 with12-bit I/O 600 Msps sampling for handling 32 upstream and downstreamOFDM channels. To this end, modem 200 HSIF may support two lanes forlegacy quadrature amplitude modulation (QAM) DOCSIS channels between AFE210 and digital radio 220, another three lanes for 14-bit 250 Msps I/Osamples to transmit two OFDM channels in the downstream.

As an example, digital radio processor 220 may be implemented in someembodiments, as a System on a Chip (SoC) which includes PHY layerfunctionality 226, e.g., PHY layer digital demodulation and decodingand, optionally, medium access control (MAC) layer 250 supportingnetworking functionality. The analog front end (AFE) 210, in certainembodiments, may comprise a full spectrum sampling tuner that integrateslow noise amplifier (LNA)/automatic gain control (AGC), analog/digitalconverters (ADCs/DACs), channelizers, power amplifiers, mixer, localoscillator (LO), phase locked loop(s) (PLL), etc., although specificfunctionalities of the AFE and digital radio processor may be modifiedto a designer's discretion. High-speed Serial Interface (HSIF) 224 is asystem and protocol that carries digital data between analog front end(AFE) 210 and digital tuner 220 and vice versa.

In various embodiments, the HSIF serial interface 224 provides a digitaltransmission scheme which streams a plurality of 8b/10b encoded framesbi-directionally and which are constantly transmitted between AFE 210and digital radio 220 through a serial bus connection (i.e., one in eachdirection, or “bi-directionally”). In one example embodiment, there aretwo types of frames send bi-directionally: a data frame; and a statusframe. Status frames can be used either to deliver status informationbetween AFE 210 and digital tuner 220, or to serve as filler. In someembodiments, status frames may be used as fillers which are insertedasynchronously into the stream of frames to match the data rate to theHSIF serial rate (i.e. when there is no available data frame ready fortransmission, a status frame is sent as a filler frame instead).

FIG. 3 shows an example process 300 high speed serial interfacecommunications in an OFDM transceiver between an analog front end anddigital radio processor may include forming 305 data and status framesto be transferred between the AFE and the digital radio, the data andstatus frames including a 10-bit comma sync word to identify the type offrame being sent, and for data frames, attaching a payload of aplurality of data samples (e.g., I/O digital samples in the downstreamand digital data in the upstream). If 310 there is data or commands tobe transferred in either direction, the data/command is placed inpayloads of the frames and sent 315 over a bi-directional serialconnection between AFE and digital radio. In preferred embodiments, datais transferred 315 in order of least significant bit (LSB) to mostsignificant bit (MSB), with status frames transferred 315 periodicallybetween data frames. If 310 no data is available for transfer, e.g.,data frames are completed 315, status frames may be sent 330, preferablyasynchronously, as filler frames between AFE and digital radio to matethe overall data throughput rate of the modem. In this manner, framesare continuously transferred through the HSIF so the overall OFDMtransceiver data rate is matched by the high-speed serial interface.

Turning to FIG. 4, a more specific example embodiment of a communicationdevice 400 operative to send/receive OFDM signals and compose andtransfer data and status frames as discussed above, includes an analogfront end (AFE) 410 for receiving and transmitting OFDM signals. Incertain embodiments the AFE 410 includes a front end analog to digitaldownconverter 413 for analog down conversion of received OFDM signals, adownstream (D/S) framer 414 and a serializer 415, the framer andserializer configured to frame and serialize the down converted digitalsamples and transfer them to digital radio circuit 420 in the frameformats and protocols discussed herein. In certain embodiments AFE 410may further include an upstream (U/S) circuit portion having adeserializer 416, a deframer 417 and an upconverter 418, including adigital-to-analog converter (DAC) and programmable gain amplifier (PGA),operative to deserialize, deframe and upconvert digital data receivedfrom digital radio/tuner circuit 420 to analog form to send OFDMcommunications from modem 400.

Similarly, digital radio 420 may include a deserializer 422, a deframer423 and downstream digital processing module 424 to process deframeddigital I/O samples from AFE 210. Additionally, digital radio 420 mayinclude upstream processing module 425, framer 426 and serializer 427for passing digital data to AFE 410 for transmission in OFDM channels.It is noted, that while various functional block items may be shownseparately for functional understanding, actual components or circuitrymay be combined in a same element. For example, a ser/des circuit may bea single circuit though depicted separately in FIG. 4 similar to otherfunctional block elements in AFE 210 and digital radio processor 220 aswould be understood by one of ordinary skill in the art.

Referring to FIGS. 5-8, according to certain example embodiments,upstream and downstream frames 500, 600, 700, 800, consist of a 10 bitK.28 Comma Sync word followed by a payload. In various embodiments,different K.28 words are used to distinguish between data (e.g., K28.5)and status (e.g., K28.1) frames. Also, in certain preferred embodiments,payloads of data frames are encoded using a standard 10/8-bit encoding.Therefore, the total length of frames (in bits) of these embodiments, isalways a multiple of 10 (or 8 before encoding). In preferredembodiments, frames are fed least significant bit (LSB) first, to mostsignificant bit (MSB) last, over a serial bus where Bit 0 refers to theLSB. Table 1 below shows an example embodiment for frame structure.

TABLE 1 HSIF Basic Frame Structure 8-bit words Name Content Description1 Sync Sync placeholder. To be Comma symbol is always the converted to10 bit K28.5 or first data in the stream. K28.5 K28.1 symbol is for DataFrame. K28.1 is for Status Frame 1 Header Packet Information such asBits 7, 6 indicate that this Data/Status, Valid/Invalid, frame is DataFrame (11) or Reserved. Status Frame (00). Bit 5 is Validity bit. Bit 5= 1 is for a Valid packet, Bit 5 = 0 is for Invalid packet. Bit 4 isframe parity indication bit. Bit 4 = 1 is for black frame. Bit 4 = 0 isfor white frame Bit 3 is reserved for DAC turn and turn off signalingPayload Payload Data Payload 2 Parity Cyclic Redundancy Check Either CRCor RS encoding (RC)16 or Reed Solomon covering the data bytes from (RS)encoding Header byte to the end of the payload.

Frame synchronization is achieved when the K.28 comma symbols are foundin their nominal position S1 times sequentially, where S1 is preferablya programmable value. The nominal position (S1) may depend on the mix ofthe data and status frames in the stream. The frame synchronization mayconsidered to be lost when the frame synchronization symbol is notdetected a specific number of times (S2) in a specified number ofconsecutive frames (S3), wherein S2 and S3 also preferably programmable.In certain preferred embodiments, an error in the sync word will notcause sync loss or packet loss.

In certain example embodiments, the payload of the frames may befollowed by redundant bytes, which can be used for error detectionand/or error correction. Example options of error detection/correction,referred to herein as “parity check” may include, cyclic redundancycheck (CRC) that allows for frame detection only, or Reed Solomonforward error correction (FEC) block code, that will enable framecorrection and/or detection. The specific parity check selected is inthe discretion of the network architect based on the desired complexityand results.

Downstream Channelized Data Structure and Framing

An example embodiment of downstream data frame 500 is shown in FIG. 5.Here, the payload of the data frame 500 includes the complex basebandsamples of two downstream RF OFDM channels sent through three logicallanes. Each logical lane carries I and Q samples of the two OFDMchannels per assignment pattern in Table 2 below.

TABLE 2 Sample arrangement of 2 OFDM channels over 3 logical lanes(Channel 1 samples = numbers; Channel 2 samples = letters) Lane 1 1 3 46 — — — Lane 2 2 B 5 e — — — Lane3 a C d f — — —

The data rate for each channel is equal to 250 mega samples per second(Msps) per I as well as per Q of each channel. The rate of the complexsamples rate over each logical lane is 250*2 channels/3 lanes Msps. Incertain preferred embodiments, the format is 2's compliment. In case acertain channel is not active, zeros are transmitted instead of samples.

Assignment between the physical lanes to logical designations of Lane 1,Lane 2, Lane 3 should preferably be configurable on both the serialinterface transmitter and receiver of the AFE and the digital radio.

Frame start times at the transmitter may preferably be aligned, andshould start with the same color indication (e.g., black or white). Datasamples are sent sequentially, while the color indication is toggled(e.g., black, white, black, white, etc.). The color of a frame isindicated in the header. In some preferred embodiments, the receiverwill ensure that frames from the three lanes belong to the same color.It is assumed that skew between lanes will never be large enough to skipa frame.

Downstream data and status frame contents are shown in FIGS. 5 and 6 aswell as Tables 3 and 4 below:

TABLE 3 Downstream (DS) Data Frame Format 8-bit words ContentDescription 1 Sync Data Frame Sync 1 Header Data Frame Header. LSBfirst, MSB last. 238 68 I/Q pairs of samples 14 bits per sample. Ifirst, Q second. LSB first, MSB last. Per pattern on Error! Referencesource not found.. 2 Parity Cyclic Redundancy Check (CRD) or ReedSolomon Forward Error Correction (FEC) Block Encoding

FIG. 6 shows an illustrative example of a downstream status frame 600according to various embodiments. Frame 600 may include the details inTable 4 below:

TABLE 4 Downstream (DS) Status Frame Format Bytes Name Description 1Sync Status Frame Sync 1 Header Status Frame Header 10 Reserved[Currently Unused, filled with zeros] 2 Parity Cyclic Redundancy Check(CRC) or Reed Solomon Forward Error Correction (FEC) Block Encoding

Each 8 bit word (Sync, Header and Parity) is also fed LSB first, MSBlast. In some embodiments, the ratio of the data/status frames is 5:1when the status frame size is 14.

Half Rate Mode (HM):

In Half Rate Mode, in one embodiment, the SerDes rate is 3 Gbps, halfthe rate of the Full Mode. The rate of the samples sent over each lanein this embodiment is equal to 250/3 Msps, which is exactly half of therate of the Full Mode. The Half Rate frame structure is equal tostructure for the Full Rate mode, except that the stuffing of samplesinto the payload of data frames is different as shown in Table 5 becauseonly one OFDM channel is being framed.

TABLE 5 Half Rate Channel to Lane Designation Lane 1 1 4 7 10 — — — Lane2 2 5 8 11 — — — Lane 3 3 6 9 12 — — —

Upstream DAC Data Structure and Framing

Example embodiments of upstream data frames 700 and status frames 800are illustrated in FIGS. 7 and 8, respectively. In the upstreamdirection, samples are sent over the HSIF at a rate of 600 Msps, 15 bitsamples, 710. These upstream samples comprise a signal that includes allof the upstream channels modulated on their corresponding RF frequenciesinside the upstream range. This data can be subsequently fed directly tothe DAC for controlling (via status frame commands 810, 812) and analogupconversion into OFDM RF channels (via data frames) by the AFE afterdeserializing and deframing through the high-speed serial interface.

In certain preferred embodiments for upstream Full Mode, all the samplesfrom the digital radio are framed, serialized and sent through a twoserial lanes, such that the odd samples are sent to one serial lane andthe even samples are sent to the second serial lane. The AFE HSIFreceiver preferably has a software programmable option to configurewhich lane is odd or even for upstream sampling. When not transmittingany data, the HSIF upstream (U/S) will send status frames as fillers.Again, the constant frame transmission upstream, with filler frames sentasynchronously when no data samples are needed to be sent, enables theHSIF transmission rate to match the overall upstream data rate.

In FIG. 7, an example upstream data frame 700 may include theinformation shown in Table 6 below:

TABLE 6 U/S Data Frame Format 8-bit words Name Description 1 Sync DataFrame Sync 1 Header Data Frame Header. LSB first, MSB last. 120 DataSamples FM: 64 even or odd consecutive 15-bit samples Each 15 bit sampleis fed LSB first, MSB last. DFM: 64 consecutive 15-bits samples 2 ParityCRC or RS FEC

In FIG. 8, an example upstream status frame 800 may include theinformation shown in Table 6 below:

TABLE 7 U/S Status Frame Format Bytes Name Description 1 Sync StatusFrame Sync 1 Header Status Frame Header 6 Reserved [filled with zeros] 1POWER MODE A command to the AFE to enter a COMMAND certain Power SavingMode. 1 PGA GAIN Describes the last Gain that was sent to the PGAthrough a dedicated serial interface 2 Parity CRC or RS FEC

According to certain embodiments, the upstream ratio of data/statusframes is 3:1, when Status frame size is 12.

Decimated Half and Full Modes

In half mode framing and channel to logical lane assignments areidentical except that the sample rate is scaled to 300 Msps. Indecimated Full Mode samples are sent at 300 Msps over one lane.

The foregoing description of architecture and processing may beimplemented as a system on a chip (SoC) receiver for cable modems usingDOCSIS 3.1 Hybrid Fiber Coax OFDM standard although it is not limitedthereto. Specific hardware and software implementations for high-speedserial interface embodiments discussed herein, may include designs inapplication specific integrated circuits (ASICs), micro-controllers,digital signal processors (DSPs), programmable logic arrays, and/or assoftware/firmware to perform the processes described herein. In oneexample embodiment, filter switching signal, synchronization andmessaging may be programmed in software instructions and executed, orcaused to be when in operation, by a processor, or central processingunit (CPU) attached to the hardware demodulator, AFE and/ordistributed/dedicated processing engine.

Referring to FIG. 9, an example functional block diagram of a modem 900for OFDM communications with HSIF may include a receive interface 902adapted to receive a wired or wireless DOCSIS 3.1 OFDM signal into themodem, an analog front end 905 and digital radio 910 connected to AFE905 via a high-speed serial interface (HSIF) providing for the OFDM andlegacy QAM channels as described herein.

In certain example embodiments, modem 900 may further include variousother functional elements such as data link layer management circuit forpacketization, managing flow control and higher layer levels of the OSIcommunications model, a processor/memory 912 adapted to control orprovide processing/storage for various functional elements of modem 900as desired. Furthermore, modem 900 may include security functionality916 and client/user interface functionality 914, such as 10-100 Gb basedEthernet PHY/MAC processing and respective interface(s) to provide auser TCP/IP layer interface connectivity. It should be understood thatmodem 900 is only a representational functional example and variousadditional functionalities may be included as desired or thosefunctionalities shown omitted if not needed or desired as known by oneof ordinary skill in the art. Thus the specific example depicted anddescribed is not intended to limit the embodiments of the invention inany manner.

DOCSIS 3.1 OFDM has been engineered by CableLabs and partners toincrease the multi-gigabit data era on existing Hybrid Fiber-Coax (HFC)networks through improved spectral efficiency. Those of skill in the artwould recognize modifications and substitutions of the elements,components and circuits described herein and possible and the inventionis not limited to the specific examples in the detailed description butrather by the appended claims.

Example Embodiments

In a First Example Embodiments, a communication device in an orthogonalfrequency division multiplexing (OFDM) enabled modem having an analogfront end (AFE) and a digital radio may include: the AFE configured tosend and receive OFDM modem channels, down convert received OFDMchannels into a plurality of I and Q digital samples, the AFE includinga high-speed serial interface (HSIF) to communicate the plurality ofOFDM I and Q digital samples to the digital radio by continuallygenerating and transferring downstream frames to the digital radio,wherein the downstream frames include data frames and status framescomprising a K.28 Comma Sync word followed by a payload.

According to a Second Embodiment, the communication device the FirstEmbodiment is furthered wherein each frame comprises a plurality of8/10b encoded words.

A Third Embodiment further defines the First wherein said downstreamdata frames include a frame sync, a header, 238 data payload words eachincluding 68 I and Q digital sample pairs and wherein said downstreamdata frames including an error detection portion at their end.

A Fourth Embodiment may further define the Third wherein the errordetection portion comprises one of a cyclic redundancy check (CRC) orReed Solomon (RS) forward error correction block code.

A Fifth Embodiment further defines the First Embodiment wherein the HSIFof the AFE comprises a framer/deframer and a serializer/deserializer.

According to a Sixth Embodiment, the First Embodiment further includesthe digitial radio including a second HSIF comprising a secondframer/deframer and a second serializer/deserializer.

In a Seventh Embodiment, the First Embodiment further is defined whereinthe AFE and HSIF are configured to down convert two downstream OFDMchannels at a 6 gigabit per second (Gbps) serial rate transfer to thedigital radio in a full rate mode (FM).

In an Eighth Embodiment, the First Embodiment is furthered wherein theAFE and HSIF are configured to down convert one downstream OFDM channelat a 3 Gbps serial rate transfer to the digital radio in a half ratemode (HM).

According to a Ninth Embodiment, a device configured to communicateorthogonal frequency division multiplexed (OFDM) signals upstream anddownstream with a network, the device including: a digital radioincluding a high speed serial interface (HSIF) to receive digitalsamples of two OFDM downstream radio frequency (RF) channels and digitalsamples of two downstream quadrature amplitude modulated (QAM) channelsfrom a separately provided analog front end (AFE), the HSIF sending andreceiving constant frames over a bi-directional serial connection to andfrom the AFE in the form of status and data frames, said status and dataframes comprising a K.28 Comma Sync Word and a payload.

In a Tenth Embodiment, the Ninth Embodiment is furthered, wherein eachframe comprises a plurality of 8/10b encoded words and wherein a K28.5identifies the data frames and K28.1 identifies status frames.

An Eleventh Embodiment further defines the Ninth, wherein saiddownstream data frames include a frame sync, a header, 238 data payloadwords each including 68 I and Q digital sample pairs and wherein saiddownstream data frames including an error detection portion at theirend.

A Twelfth Embodiment further adds to the Eleventh Embodiment wherein theerror detection portion comprises one of a cyclic redundancy check (CRC)or Reed Solomon (RS) forward error correction block code.

According to a Thirteenth Embodiment, the Ninth Embodiment is furthered,wherein the HSIF of the digital radio comprises a framer/deframer and aserializer/deserializer.

A Fourteen Embodiment further defines the Thirteenth by including theAFE including a second HSIF comprising a second framer/deframer and asecond serializer/deserializer.

A Fifteenth Embodiment furthers the Ninth, wherein the digital radio andHSIF are configured to sample, frame and serialize upstream data to sendto the AFE at a 600 Mega samples per second (Msps) rate for 15-bit realsamples fed least significant bit (LSB) first to most significant bit(MSB).

A Sixteenth Embodiment includes a method for communicating data in acable modem using a high-speed serial interface (HSIF), the methodincluding: forming downstream frames comprising a K28 Comma word and apayload; and continually transferring the formed downstream framesincluding status frames and data frames, the data frames includingcomplex baseband samples for OFDM channels received by said cable modemin their payload, wherein when no data is needed to be transferred,status frames are inserted asynchronously as filler frames.

A Seventeenth Embodiment furthers the Sixteenth, wherein the OFDMchannels received by said cable modem are compliant with a Data OverCable System Interface Specification (DOCSIS) 3.1 standard.

An Eighteenth Embodiment furthers the method of the Seventeenth byfurther including receiving upstream frames continuously, said upstreamframes including status and data frames, wherein said upstream dataframes include 15 bit-data samples in their payloads.

According to a Nineteenth Embodiment, either the First or SecondEmbodiments are furthered, wherein said downstream data frames include aframe sync, a header, 238 data payload words each including 68 I and Qdigital sample pairs and wherein said downstream data frames includingan error detection portion at their end.

In a Twentieth Embodiment, the First through Third and NineteenthEmbodiment may be furthered, wherein the HSIF of the AFE comprises aframer/deframer and a serializer/deserializer.

A Twenty-First Embodiment may include any of the First through Third orNineteenth through Twentieth Embodiments of a device that furtherincludes: the digitial radio including a second HSIF comprising a secondframer/deframer and a second serializer/deserializer.

According to a Twenty-Second Embodiment, the First through Third orNineteenth through Twenty-First Embodiments may be further defined,wherein the AFE and HSIF are configured to down convert two downstreamOFDM channels at a 6 gigabit per second (Gbps) serial rate transfer tothe digital radio in a full rate mode (FM).

A Twenty-Third Embodiment may further define the First through Third orNineteenth through Twenty-Second Embodiments, wherein the AFE and HSIFare configured to down convert one downstream OFDM channel at a 3 Gbpsserial rate transfer to the digital radio in a half rate mode (HM).

In a Twenty-Fourth Embodiment, the Ninth through Twelfth Embodiments arefurther defined, wherein the HSIF of the digital radio comprises aframer/deframer and a serializer/deserializer.

A Twenty-Fifth Embodiment further defines the Thirteenth by includingthe AFE and having a second HSIF comprising a second framer/deframer anda second serializer/deserializer.

According to a Twenty-Sixth Embodiment, a device for communicating datain a cable modem using a high-speed serial interface (HSIF), the devicecomprising: means for forming downstream frames comprising a K28 Commaword and a payload; and means for continually transferring the formeddownstream frames including status frames and data frames, the dataframes including complex baseband samples for OFDM channels received bysaid cable modem in their payload, wherein when no data is needed to betransferred, status frames are inserted asynchronously as filler frames.

A Twenty-Seventh Embodiment further defines the device of theTwenty-Sixth Embodiment by including means for receiving upstream framescontinuously, said upstream frames including status and data frames,wherein said upstream data frames include 15 bit-data samples in theirpayloads.

A Twenty-Eighth Embodiment further defines those of the Third andEleventh Embodiments, wherein the error detection portion comprises oneof a cyclic redundancy check (CRC) or Reed Solomon (RS) forward errorcorrection block code.

According to a Twenty-Ninth Embodiment the embodiments of any one of theFirst through Fourth Embodiments is furthered wherein the HSIF of theAFE comprises a framer/deframer and a serializer/deserializer.

In a Thirtieth Embodiment, the device of any one of the First throughFifth and Twenty-Ninth Embodiments further includes: the digitial radioincluding a second HSIF comprising a second framer/deframer and a secondserializer/deserializer.

A Thirty-First Embodiment may further any of the First through Fifth andThirtieth Embodiments, wherein the AFE and HSIF are configured to downconvert two downstream OFDM channels at a 6 gigabit per second (Gbps)serial rate transfer to the digital radio in a full rate mode (FM).

A Thirty-Second Embodiment furthers any one of the First through Fifthand Twenty Ninth through Thirty-First Embodiments, wherein the AFE andHSIF are configured to down convert one downstream OFDM channel at a 3Gbps serial rate transfer to the digital radio in a half rate mode (HM).

A Thirty-Third Embodiment furthers the First through Fifteenth andNineteenth through Thirty-Second Embodiments, wherein said cable modemis compliant with a Data Over Cable Service Interface Specification(DOCSIS) 3.1 standard.

A Thirty-Fourth Embodiment furthers any of the First through Fifteenthand Nineteenth through Thirty-Third Embodiments, wherein the digitalradio comprises a System on a Chip (SoC) coupled to the AFE via abi-directional serial interface.

Disclaimer: The present disclosure has been described with reference tothe attached drawing figures, with certain example terms and whereinlike reference numerals are used to refer to like elements throughout.The illustrated structures, devices and methods are not intended to bedrawn to scale, or as any specific circuit or any in any way other thanas functional block diagrams to illustrate certain features, advantagesand enabling disclosure of the inventive embodiments and theirillustration and description is not intended to be limiting in anymanner in respect to the appended claims that follow, with the exceptionof 35 USC 112, sixth paragraph claims using the literal words “meansfor,” if present in a claim.

As utilized herein, the terms “component,” “system,” “interface,”“logic,” “circuit,” “device,” and the like are intended only to refer toa basic functional entity such as hardware, software (e.g., inexecution), logic (circuits or programmable, firmware alone or incombination to suit the claimed functionalities. For example, acomponent, module, device or processing unit may mean a microprocessor,a controller, a programmable logic array and/or a circuit coupledthereto or other logic processing device, and a method or process maymean instructions running on a processor, firmware programmed in acontroller, an object, an executable, a program, a storage deviceincluding instructions to be executed, a computer, a tablet PC and/or amobile phone with a processing device.

By way of illustration, a process, logic, method or module can be anyanalog circuit, digital processing circuit or combination thereof. Oneor more circuits or modules can reside within a process, and a modulecan be localized as a physical circuit, a programmable array, aprocessor. Furthermore, elements, circuits, components, modules andprocesses/methods may be hardware or software, combined with aprocessor, executable from various computer readable storage mediahaving executable instructions and/or data stored thereon. Those ofordinary skill in the art will recognize various ways to implement thelogical descriptions of the appended claims and their interpretationshould not be limited to any example or enabling description, depictionor layout described above, in the abstract or in the drawing figures.

1. A communication device in an orthogonal frequency divisionmultiplexing (OFDM) enabled modem having an analog front end (AFE) and adigital radio, the communication device comprising: the AFE configuredto send and receive OFDM modem channels, down convert received OFDMchannels into a plurality of I and Q digital samples, the AFE includinga high-speed serial interface (HSIF) to communicate the plurality ofOFDM I and Q digital samples to the digital radio by continuallygenerating and transferring downstream frames to the digital radio,wherein the downstream frames include data frames and status framescomprising a K.28 Comma Sync word followed by a payload.
 2. Thecommunication device of claim 1 wherein each frame comprises a pluralityof 8/10b encoded words.
 3. The communication device of claim 1 whereinsaid downstream data frames include a frame sync, a header, 238 datapayload words each including 68 I and Q digital sample pairs and whereinsaid downstream data frames including an error detection portion attheir end.
 4. The communication device of claim 3 wherein the errordetection portion comprises one of a cyclic redundancy check (CRC) orReed Solomon (RS) forward error correction block code.
 5. Thecommunication device of claim 1 wherein the HSIF of the AFE comprises aframer/deframer and a serializer/deserializer.
 6. The communicationdevice of claim 5 further comprising: the digitial radio including asecond HSIF comprising a second framer/deframer and a secondserializer/deserializer.
 7. The communication device of claim 1 whereinthe AFE and HSIF are configured to down convert two downstream OFDMchannels at a 6 gigabit per second (Gbps) serial rate transfer to thedigital radio in a full rate mode (FM).
 8. The communication device ofclaim 1 wherein the AFE and HSIF are configured to down convert onedownstream OFDM channel at a 3 Gbps serial rate transfer to the digitalradio in a half rate mode (HM).
 9. The communication device of claim 6wherein the digital radio comprises a System on a Chip (SoC) coupled tothe AFE via a bi-directional serial interface.
 10. The communicationdevice of claim 1 wherein the OFDM-enabled modem is compliant with aData Over Cable Service Interface Specification (DOCSIS) 3.1.
 11. Adevice configured to communicate orthogonal frequency divisionmultiplexed (OFDM) signals upstream and downstream with a network, thedevice comprising: a digital radio including a high speed serialinterface (HSIF) to receive digital samples of two OFDM downstream radiofrequency (RF) channels and digital samples of two downstream quadratureamplitude modulated (QAM) channels from a separately provided analogfront end (AFE), the HSIF sending and receiving constant frames over abi-directional serial connection to and from the AFE in the form ofstatus and data frames, said status and data frames comprising a K.28Comma Sync Word and a payload.
 12. The device of claim 11 wherein eachframe comprises a plurality of 8/10b encoded words and wherein a K28.5identifies the data frames and K28.1 identifies status frames.
 13. Thedevice of claim 11 wherein said downstream data frames include a framesync, a header, 238 data payload words each including 68 I and Q digitalsample pairs and wherein said downstream data frames including an errordetection portion at their end.
 14. The device of claim 13 wherein theerror detection portion comprises one of a cyclic redundancy check (CRC)or Reed Solomon (RS) forward error correction block code.
 15. The deviceof claim 11 wherein the HSIF of the digital radio comprises aframer/deframer and a serializer/deserializer.
 16. The device of claim15 further comprising: the AFE including a second HSIF comprising asecond framer/deframer and a second serializer/deserializer.
 17. Thedevice of claim 11 wherein the digital radio and HSIF are configured tosample, frame and serialize upstream data to send to the AFE at a 600Mega samples per second (Msps) rate for 15-bit real samples fed leastsignificant bit (LSB) first to most significant bit (MSB).
 18. Thedevice of claim 16 wherein the digital radio comprises a System on aChip (SoC) coupled to the AFE via a bi-directional serial interface. 19.The device of claim 18 wherein the device comprises a cable modemcompliant with a Data Over Cable Service Interface Specification(DOCSIS) 3.1 standard.
 20. A method for communicating data in a cablemodem using a high-speed serial interface (HSIF), the method comprising:forming downstream frames comprising a K28 Comma word and a payload;continually transferring the formed downstream frames including statusframes and data frames, the data frames including complex basebandsamples for OFDM channels received by said cable modem in their payload,wherein when no data is needed to be transferred, status frames areinserted asynchronously as filler frames.
 21. The method of claim 20wherein the OFDM channels received by said cable modem are compliantwith a Data Over Cable Service Interface Specification (DOCSIS) 3.1standard.
 22. The method of claim 21 further comprising: receivingupstream frames continuously, said upstream frames including status anddata frames, wherein said upstream data frames include 15 bit-datasamples in their payloads.